As is known in the art, one type of conventional electrical current sensor uses a Hall effect magnetic field transducer in proximity to a current-carrying conductor. The Hall effect device generates an output signal having a magnitude proportional to the magnetic field induced by the current through the conductor. Typical current sensors of this type include a gapped toroid magnetic flux concentrator, with the Hall effect device positioned in the toroid gap. The Hall effect device and toroid are assembled in a housing, which is mountable on a printed circuit board. In use, a separate current-carrying conductor, such as a wire, is passed through the center of the toroid and is soldered to the printed circuit board, such as by soldering exposed ends of the wire to plated through-holes. Such devices tend to be undesirably large, both in terms of height and circuit board area.
Various parameters characterize the performance of Hall effect devices in current sensing applications, including sensitivity, which is the change in the output signal of the Hall effect device in response to a one ampere change through the conductor, and linearity, which is the degree to which the output signal varies in direct proportion to the current through the conductor. Important considerations in the use of Hall effect devices include the effect of stray magnetic fields and external magnetic noise on the device performance. Another important consideration is the effect of electromagnetic noise upon the device performance.
It has also been found, in general, that accumulated charge can form at an interface between an integrated circuit encapsulation (e.g., plastic) and the substrate (sensor die) of the integrated circuit. This trapped charge tends to cause undesirable effects, for example “gate leakage” from the substrate of the integrated circuit, resulting in out-of-specification behavior of the integrated circuit. The “gate leakage” can be caused by a forward biased enhancement mode parasitic field effect transistor (FET), which forms due to accumulated charge over a floating epi-material pocket in the substrate of the integrated circuit.